One of the most popular accessories for trucks and recreational vehicles is a truck box used to store and secure a variety of tools and other items. One type of truck box is a cross-over box which comprises a front wall, a back wall, a bottom wall and opposed end walls which are interconnected to form a hollow interior. The truck box interior is closed by a top wall or lid pivotal between open and closed positions on a hinge mounted to the back wall, usually with the assistance of gas springs. Each of the end walls of a cross-over box is formed with a wing extension which rests atop the side walls of a pickup truck, for example, where it may be connected by clamps or other fastening devices to secure the box in place within the truck bed.
Cross-over boxes are typically made of aluminum tread plate or a similar material which can undergo bending and welding operations in the fabrication process. With reference to FIGS. 1-5 of the drawings, labeled “Prior Art,” several views are provided depicting a cross-over truck box 10 constructed using conventional prior art fabrication techniques. Initially, a sheet 12 of tread plate undergoes a bending operation in which it is formed into a tub 14 having a bottom wall 16 joined to upright side walls 18, 20 collectively defining an interior 22 open at the top and opposite ends. The end walls 24, 26 of the box 10 are each formed in a bending operation from a sheet 28 of tread plate and have a wing extension 30. In order to close the ends of the tub 14, each end wall 24, 26 is positioned at one end and welded in place, e.g. a weld is required along the length of the side edges of each end wall 24, 26 and the end edges of the tub side walls 18, 20, and, along the bottom edge of each end wall 24, 26 and opposed end edges of the bottom wall 16 of tub 14. Further, to provide a secure connection between the side walls 18, 20 of the tub 14 and the wing extension 30 of each end wall 24, 26, each side wall 18, 20 is preferably formed with an outwardly extending arm 32 at opposite ends. These arms 32 extend along one side of each wing extension 30 where they are welded in place.
The method of fabrication used to manufacture cross-over truck boxes described above is labor-intensive and relatively expensive considering all of the welds required to connect the end walls 24, 26 to the tub 14. Further, as best seen in FIG. 1, a section 34 of material at both ends of the sheet 12 forming tub 14 must be removed prior to the bending operation in order to form the arms 32 which connect to the end wall wing extensions 30. This drop loss is significant and represents an appreciable amount of lost revenue for manufacturers of truck boxes using such prior art fabrication method, given the high cost of aluminum tread plate.